Naphthalenes from Hemerocallis middendorffii with the antioxidant and anticomplementary activities of its compounds

One new naphthalene named as naphthalenone D (1), together with four known analogues (2–5), were isolated from the flowers of Hemerocallis middendorffii. The new compound was identified as 7-acetyl-8-hydroxy-6-methyl-4S-β-glucoside-1-tetralone by spectroscopic methods, including 2D-NMR techniques. The known compounds were determined spectroscopically and compared with previously reported spectral data. All compounds exhibited significant antioxidant activity and anticomplementary effects against the classical pathway (CP) with CH50 values from 0.41 mM to 4.22 mM. These results suggest their potential as promising candidates for antioxidant and anticomplement agents.